Muon transverse polarization in $$K_{l2_\gamma } $$ decay due to the electromagnetic final-state interaction

For the decay process K + → μ + νγ, the effect of muon transverse polarization caused by electromagnetic final-state interaction is analyzed. It is shown that, in the one-loop approximation, the muon transverse polarization varies from −1.3×10−3 to zero in the region of the Dalitz plot. The mean value of the muon polarization, 〈P T〉, in the kinematical region E γ ≥20 MeV is −5.44×10−4.